#include<iostream>
#include<cstring>
using namespace std;
#define maxlen 1000
class big{
    private:
    int length;
    int arr[maxlen];

    public:
    big(int num=0){
        memset(arr,0,sizeof(arr));
        for(this->length=1;num;length++){
            arr[length]=num%10;
            num/=10;
        }
        length-=1;
    }
    void flatten(){
        for(int i=1;i<maxlen;i++){
            arr[i+1]+=arr[i]/10;
            arr[i]%=10;
        }
        length=maxlen-1;
        while(!arr[length]){
            --length;
        }
    }
    void print(){
        for(int i=max(1,length);i>=1;i--){
            cout<<arr[i];
        }
    }
    int&operator[](int i){
        return arr[i];
    }
    big operator+(big&num){
        big ans;
        for(int i=1;i<maxlen;i++){
            ans[i]=num[i]+arr[i];
        }
        ans.flatten();
        return ans;
    }
};

big arr[2020];

int main(){
    big one(1);
    arr[0]=one;
    int a,b;
    cin>>a>>b;b=b-a;
    for(int i=0;i<b;i++){
        arr[i+1]=arr[i+1]+arr[i];
        arr[i+2]=arr[i+2]+arr[i];
    }
    arr[b].print();
}